Gekko
A Gekko (ゲッコー, Gekkō) is a possessed frog-like mini-boss that guards two of four temples in Majora's Mask.
The first one is found in Woodfall Temple. It rides the back of a Snapper. Once the Snapper is killed, this creature will run along the walls of the room. Shoot it with your bow.
The second Gekko, in the Great Bay Temple, will hang to the ceiling in a bubble of Mad Jelly, a simple Ice Arrow should stop that, sending it sailing down to the floor. Shoot it, and repeat. If Link fails to shoot the Gekko, or gets to close to the bubbles, he will be trapped inside. The Gekko will then punch Link repeatedly causing damage. It then finishes it off with a mighty left hook, that breaks Link through the bubble, causing serious damage.
After you defeat each of the amphibious creatures, they will in turn change into one of the frogs in Don Gero's Frog Choir each.